Would appreciate suggestions for small trees whose mature roots are unlikely to cause damage when planted in retaining walls that are overtop of underground parking (in a condo). This specific situation: 'planter' is 10feet x 16feet and 22 inches high; no bottom; 2" drain rock + 20" garden soil; built directly on the concrete surface with parking below. Similar 'planters' on the property (same height but larger length&width) were planted many years ago with large shade trees (flowering cherries, maples, etc) and these mature trees have caused leaks into the underground parking (no surprise). Also, a fair number have died. We are wanting the look and feel of shade trees without the ensuing problems in future years. I have chosen two trees: Acer Shirasawanum 'Aureum', the label indicates mature size is 15'tall x 10'wide. Also a pink flowering dogwood - am turning the house and yard over to find the misplaced ID tag - it is smaller growing (as far as flowering dogwoods go) and an improved variety (as far as problems experienced by pink dogwoods go). Are there any fast growing shrubs that could be pruned up into a tree-like appearance that would have small mature root systems. (Rose of Sharon??). Not Rhododenderons - the property already has more than most of the condo owners can appreciate. Any tree or large shrub suggestions would be appreciated. Thank You Irm
Your strata was engineered to withstand the weight of the previous trees. As well, the original shrub material was chosen by a registered landscape designer who specifically selects plant material that is suitable for your strata. They have to consider how large and heavy trees and shrubs are when they grow to maturity. Every-thing is approved by your City Hall. Most tree roots spread out at least as wide as the drip line if not further, unless they are held in containers or bunkers such as you have. Most tree roots will generally not go deeper than 18 inches. The majority of trees do not have tap roots. If your garage was leaking, it is most likely that the membrane is leaking or the drainage is plugged. Hiring a certified ISA arborist or a certified horticulturist from your area would be money well spent.
Yeah, I doubt the trees caused the leakage. Figure anything planted will have a much bigger root system than the top, this is usual. Not that the size of the roots necessarily needs to be considered, other than choosing things small enough to remain viable in the soil space available. Naturally you would not try to grow forest giants in such a situation. Size of planter described should suit one vine maple or one dwarf flowering crabapple or one service-berry or...
Thank you both, for your replies. I will pass this info on to strata; will be their decision whether to use the 2 trees that I have chosen (Cornus Kousa 'Satomi') and (Acer Shirasawanum 'Aureum' - I think that is a type of vine maple?). Irm
Kousa are wide-spreading and not wild about drought, the planter will have to be kept moist in summer. You can also get leaf spot and twig blight on 'Satomi'. The golden full moon maple is a Sec. Palmata maple like vine maple but is not the same species. It must have summer shade or the leaves burn up, and like the Kousa cultivar is derived from a monsoon climate species, with little or no adaptation to serious summer drought. Unlike vine maple, western service-berry or Douglas maple.
